import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class TcpEchoServer {
    private ServerSocket socket = null;

    //这里和 UDP 服务器类似，也是在构造对象的时候，绑定端口号。
    public TcpEchoServer(int port) throws IOException {
        socket = new ServerSocket(port);
    }

    public void start() throws IOException {
        //启动服务器
        System.out.println("启动服务器");
        // 这种情况一般不会使用 fixedThreadPool, 意味着同时处理的客户端连接数目就固定了.
        ExecutorService executorService = Executors.newCachedThreadPool();

        while (true){
            //tcp 来说，需要先处理客户端发来的连接。
            //通过读写 clientSocket，和客户端进行通信
            //如果没有客户端连接，此时 accept 就会阻塞。

            Socket clientSocket = socket.accept();
            //使用多线程的方式来调整
//            Thread thread = new Thread(() -> {
//                processConnection(clientSocket);
//            });
//            thread.start();

            //使用线程池来调整
            executorService.submit(() -> {
               processConnection(clientSocket);
            });
        }
    }

    //处理一个客户端的连接
    //可能要涉及到多个客户端的请求和响应
    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s:%d] 客户端上线！\n",clientSocket.getInetAddress(),clientSocket.getPort());
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()) {
            //针对 InputStream 套了一层
            Scanner scanner = new Scanner(inputStream);
            //针对 OutputStream 套了一层
            PrintWriter writer = new PrintWriter(outputStream);

            while (true){
                //1.读取请求并解析。可以直接 read，也可以借助 Scanner 来辅助完成。
                if(!scanner.hasNext()){
                    System.out.printf("[%s:%d] 客户端下线！\n",clientSocket.getInetAddress(),clientSocket.getPort());
                    break;
                }
                String request = scanner.next();
                //2.根据请求，计算响应
                String response = process(request);
                //3.返回响应到客户端
                writer.println(response);
                writer.flush();
                //4.打印日志
                System.out.printf("[%s:%d] req:%s  resp: %s\n",clientSocket.getInetAddress(),clientSocket.getPort(),
                        request,response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            try{
                clientSocket.close();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer tcpEchoServer = new TcpEchoServer(9090);
        tcpEchoServer.start();
    }
}
